As the number of persons infected with Human Immunodeficiency Virus (HIV) reaches 2 million in the United States, there is a growing concern among occupational groups such as health care workers, first responders, sanitation workers, police and firemen that they may become infected with HIV through accidental needlesticks or splashes occurring at work. Nucleoside analogues such as Zidovudine (also referred to as AZT) are offered as prophylaxis to occupational groups following exposure to HIV contaminated materials. Use of dideoxynucleosides, such as ZDV, in healthy populations for prophylaxis has not been examined for potential reproductive or long term mutagenic effects. Such investigation is warranted given that genetic damage in humans and genetic plus reproductive effects have been reported in animals exposed to ZDV, and the data obtained would be of help to individuals and their physicians in making more informed risk/benefit decisions about the use of this type of prophylaxis following accidental occupational exposures. During the past year, a Request for Task Order was prepared by the Contract Specialist based upon the Statement of Work in our detailed Project Plan. Following a pre-proposal conference, the Clinical Centers at Duke and UNC collaborated to prepare a proposal for conduct of a cohort study which will compare individuals occupationally exposed to HIV who elect to take ZDV or other dideoxynucleoside prophylaxis therapy to a similar occupationally exposed group of individuals who do not elect this prophylaxis therapy. Cytogenetic effects in blood lymphocytes and both fertility and cytogenetic parameters in sperm will be evaluated (repeated measures design). Subjects will be recruited from occupational exposures to HIV occurring in the greater Triangle area during a two year period and will be referred to the Clinical Research Study sites for specimen collection. Additionally, semen from HIV infected individuals preparing to start didioxynucleoside therapy will be obtrained pre-, during, and post- didioxynucleoside therapy and evaluated for cytogenetic and fertility effects.